Plants are characterized by their characters & character states
green
non-motile
eukaryotic & multi-cellular
walls of cellulose
alternation of generations
Diversity: There are many kinds of plants and hundreds of thousands of species
But the basic lineages of plants are fairly easy
new characters define evolution of lineages
Taxonomy
Classification is putting objects into groups
requires naming, describing, and identifying species
“science of documenting biodiversity” (Keogh, 1995)
Linnaeus founded binomial system and classification hierarchy
King Phillip Came Over From Germany Stoned
each level or unit is called a taxon w/ standardized endings
Kingdom is most inclusive group, species is least inclusive
in your generation these hierarchy may become obsolute via molecular markers
Taxonomy has predictive value…
Question: If two plants are related (i.e., in the same genus) and one of the plants is a source of food or drug, what can we assume about the second plant?
Case Study: Pacific yew (Taxus brevifolia)
Taxol: alkaloid first isolated from the bark and used to treat breast cancer
FDA approval in 1994 but the bark of 3 trees is needed for 1 patient
16,000 pounds of bark is used to produce 2.2 pounds of taxol
Search for taxol was successful in other members of the genus
has made drug more available
Nomenclature
Common names vs Scientific nomenclature
Common names have the following advantages:
often descriptive (i.e., describe some important feature)
easy to pronounce & remember (more familiar to people)
more pleasing to ear & some are fun
Why bother with scientific names?
not governed by rules, so little consistency
applied indiscriminately to various taxonomic levels (i.e. ‘Oak’)
some plants have more than one common name.
may not exists for rare species
may reflect language barriers
may be botanically incorrect (e.g. Jerusalem artichoke)
Common names vs Scienitific nomenclature
The rule book for botanical nomenclature is the International Code of Botanical Nomenclature (ICBN)
every plant gets 1 binomial name
Binomials are combos of genus name specific epithet (e.g. Quercus rubra)
Genus names are nouns that may commemorate a place, person, person, habitat, culture
Epithets are adjectives that can also be commemorative (except for you!)
Taxonomic ranks have standardized endings
Identifying a species usually requires a dichotmous key
Keys consists of paired questions (‘couplets’)
resembles choose your own adventure books
choose the statement that fits your specimen
guides you forward through selection steps
We will need to bypass this process in this class
we will utilize online tools that help
phone apps and interactive keys
I want you to learn major diagnostic characters
We must learn vegetative terminology!!
The amount of terminology used in Plant Taxonomy may, at times, seem overwhelming
A feature of a plant is called a character and the specific form of the character is a state.
First, we focus on vegetative (non-reproductive) parts
includes the 3 primary organs - leaf, root, stem
you will need many states to ID a plant!
Life span/Duration:
Annual: completes life cycle in a single year
Biennial: completes life cycle in two years
Perennial: lives more than two seasons
Evergreen: keeps its leaves year-round
Deciduous: looses its leaves at the end of growing season
Hard to determine what a herbaceous plant is…
annuals have small slender taproots, while biennials/perennials are larger.
biennials & perennials often have storage structures (bulbs)
plants with woody stems are perennials
Plant vegetative organs (only 3! plants are easy!)
Root: anchor and absorbs, underground, develop from radicle in seed
Leaf: photosynthetic organ, attached to stem, has a bud at its base
Stem - leaf-bearing organ, with buds
Some plants lack one or more of these structures
aquatic plants often lack roots and cacti lack leaves.
Leaf parts
Blade - main photosynthetic part
Petiole - a fancy term for the stalk
Stipules - appendage at base of petiole in some leaves
Stipules can be glandular, leafy, spiny, or scale-like
Often, stipules fall off after the leaf expands
Leaf structure
simple - leaf blade all one section
compound - leaf blade divided into smaller sections
leaflet - section of a compound leaf
rachis - stalk that supports leaflets in a compound leaf
on central axis
rachilla - stalk that supports lateral leaflets
pinnately compound - like a feather
palmately compound - like the fingers on your hand
Leaf Arrangement
Leaves may be found at base (e.g. dandelion), along the stem, or both
Leaves are attached at nodes:
alternate - one leaf per node
opposite - two leaves per node
whorled - more than two leaves per node; not common in temperate woody plants
Trees with opposite leaves = MADCAP HORSE
M=maple; A=ash; D=dogwood
CAP=Caprifoliaceae or Honeysuckle family
Horse = Horsechestnut and buckeye
Leaf margin
entire: margin smooth
lobed: margin with indentations
serrate: margin toothed
Singly or doubly toothed
Leaf shape: There are sooooo many
Leaf Venation
pinnate: single main vein with secondary veins branching
like a feather
palmate: several primary veins arising from a one point
parallel: primary & secondary veins parallel
Surface features
glabrous - no hairs, smooth surface
pubescent - hairy; due to trichomes
glaucous - powdery covering
scabrous - rough to the touch like sandpaper
Stem features
Node: region where leaf is attached
internode - region between nodes
axil - upper junction of leaf and stem
Bud - embryonic shoot and/or flowers
found in the leaf axil; at the base of leaf
axillary/lateral: buds along stem
terminal: buds at the end of the stem
scales: protective covering over bud
Terminal bud scale scar: left on stem where the terminal bud scales fell off